Refactor ConstantExpression/ConstantConstructor to use entities.

tests/compiler/dart2js/semantic_visitor_test_send_data.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.semantics_visitor_test;
 
 const Map<String, List<Test>> SEND_TESTS = const {
   'Parameters': const [
     // Parameters
     const Test('m(o) => o;',
@@ skipping 1528 matching lines @@
             operator: '--')),
   ],
   'Dynamic type literals': const [
     // Dynamic type literals
     const Test(
         '''
         m() => dynamic;
         ''',
         const Visit(VisitKind.VISIT_DYNAMIC_TYPE_LITERAL_GET,
             constant: 'dynamic')),
-    // TODO(johnniwinther): Update these to expect the constant to be `dynamic`
-    // instead of `Type`. Currently the compile time constant evaluator cannot
-    // detect `dynamic` as a constant subexpression.
     const Test(
         '''
         m() { dynamic(null, 42); }
         ''',
         const Visit(VisitKind.VISIT_DYNAMIC_TYPE_LITERAL_INVOKE,
-            constant: 'Type', arguments: '(null,42)')),
+            constant: 'dynamic', arguments: '(null,42)')),
     const Test(
         '''
         m() => dynamic = 42;
         ''',
         const Visit(VisitKind.VISIT_DYNAMIC_TYPE_LITERAL_SET,
             constant: 'dynamic', rhs: '42')),
     const Test(
         '''
         m() => dynamic += 42;
         ''',
@@ skipping 2731 matching lines @@
             element: 'field(a)', rhs: '42')),
 
     const Test(
         '''
         m() => unresolved ??= 42;
         ''',
         const Visit(VisitKind.VISIT_UNRESOLVED_SET_IF_NULL,
             name: 'unresolved', rhs: '42')),
   ],
 };